Concentrated fertilizers



Sept 6, 1932- A r-:. JoHNsoN I' y 1,876,501

PROCESS OF MANUFACTURING CONCENTRATED FERTILIZERS Filed Oct. 4. 1930 JMW@ Fatented Sept. 6, 1932 ERLING: JOHNSON, OF ODLDA,

STATES PATENT OFFICE PROCESS OF MANUFACTURING CONCENTRATED FERTILIZERS Application filed October 4, 1930,' Serial No. 486,507, and in Norway October 11, 1929.

In my pending patent application 391,506

I have described a process of converting phos` phate rock into soluble compounds and of separating its content of lime and phosphoric acid. According to said process the vphos phate rock is by means of nitric acid converted into a solution of calcium nitrate and free phosphoric acid and from this solution a considerable part of the calcium nitrate is 0 crystallized out, leaving a mother liquor which besides phosphoric acid contains more or less calcium nitrate and some nitric acid.

My present invention relates to a method of manufacturing concentrated universal fertilizers from said mother liquor and potassium chloride.

rThe accompanying How sheet illustrates the process. The essential steps are indicated by full lines, and the steps which may, but need not necessarily be used in the process are indicated by dotted lines. y

The invention is based upon the combination of reactions set forth below.

The phosphate rock is first dissolved in nitric acid according to the reaction leaves the prow The second portion 1s likewise subJect-ed to a crystallization but this crystallization is only carried to that extent at which sufficient calcium nitrate is still retained in the solution 1 tf forni di-calcium phosphate with the phos phoric acid of the solution. For this purpose only 1/3 of the total calcium'nitrate of the solution is removed as crystals as represented by the equation; y

leaves the process.

The mother liquor frointhe operation 2b. 1s subjected to neutralization with ammonia or ammonium carbonate according to the reaction:

Di-calcium phosphate is precipitated and is iltered off and washed. The remaining l liquid contains ammonium nitrate. 4

This solution is caused to react with potassium chloride according to the equation:

which gives a mixture of potassium nitrate and di-ammonium phosphate. The final products leaving the process are: calcium nitrate according to Equations 2a. and 2b., di-ealcium phosphate (Equation 3) ammonium chloride (Equation 4) and as main prod uct (Equation 5) a universal fertilizer containing 4 mol potassium nitrate to two mol eo iii-ammonium phosphate With the following content of plant-food components:

K 2 Relative ratio 188 parts of :O 8 per cent 1, 7

A* KNOB 142 parts of P2j05=21 (NHUZHPO 112 parts of N. :16.5 1.-

It is immediately evident that according 'to the conditions of Working that is, the degrec of crystallization of the calcium nitrate, the apportionment of mother liquor among the reactions 2a. and l2b'. and consequently according tothe quantity of di-calcium phosphate precipitated in reaction (3) the qualitity of ammoniumv nitrate converted into potaissium nitrate etc., products may be obtained in Which the ratio of plant-food coinponents may be varied at will Within wide limits.

lt is to be pointed out that in practical Work it is not possible to realize a quite complete crystallization of calcium nitrate as supposed in- Equation 2a. An output of 85 per cent of crystals is however easily reached. Yet, this fact has nodetrimental influence upon the carrying out of the process: At Worst therest of the calcium retained 1n solution may result in that some l() per cent of the phosphoric acid present in the mixed product is only citrate-soluble, While the rest of the phosphoric acid is Water-soluble. If desired the rest of the calcium may however be removed as calcium sulphate by precipitation withO sulphur-ic acid, ammonium-or potassium sulphates etc. The precipitant may be recovered. As it is only a fraction of the initial calcium content Which eventually is to be removed, no large quantities of preeipitants are necessary and need be circulated. f

The greater or smaller surplus of nitric acid, which may be present in the primary solution of phosphate rock in nitric acid enters the nal product in the shape of ammonium nitrate.

As already mentioned the relative ratio of components in the finished product may be varied at will Within Wide limits.

B lslight modiiications, of the process, products may be obtained of the following compositions Relative ratio B. BKNOs 131 parte of K2O=21 per cent 1. 3 lNHiNO: 142 parts of P2Oi=23 1.4 ZNHiHiPOi 98 parts of N. :16 1.0

ln this product 4/7 of thev nitrogen is in the form of nitrate, 3/7 in the form of ammonia.

Relative ratio O. 2KNOn 95 parts of K2O=19 per cont 1.0 0.5NH4NO3 142 parts of P2O5=28 1.5 2(NH4)2HPO4 98 parts of N. :19 1.0

the manner that the liquor by means of nose-r and such like is injected into an ammoniacal atmosphere. Under these conditions a dry neutralized product ready for use may immediately be obtained.

The neutralization' With ammonia may be continued to the di-ammonium phosphate stage or only until mono-ammonium phosphate is formed. The former is supposed inthe-products A and C above, thel latter in the product B. The neutralization may however be continued to a mixture of the two salts in any desired proportion. The composition of the nished product may vary somewhat according to special purposes and requirements. u

The (ii-calcium phosphate leaving the process may be utilized separately or it may be added to the finished compoundproduct in suitable proportions in order to augment its content of phosphoric acid by some citrate soluble one, Which may lead to fertilizers of physiologically neutral or alkaline nature.

Further compound fertilizers of physiologically alkaline reactions may be prepared separately from the di-calcium phosphate and the calcium nitrate obtained in this process. Such fertilizers free from inactive substances 4are for example obtained when the calcium nitrate from the reactions 2a. and 2?). is mixed with ycli-phosphate and potassium nitrate, to which some urea may be added in order to increase the content of nitrogen. if for example two mol of (li-calcium phosphate are mixed With two mol of potassium nitrate which are not used in Example C above and when further one mol. of calcium nitrate fromthe process and 2 mol. of urea are added a product is obtained which in the dry state has the following composition Relative on O ratio 2 l42partsoi`P2O5=1L7percent1-1 )EHBO 95 pai-twingo 11. 2 o. 5 2 128partsofN. :15.0 1. 0

2 mol. of CaHPO l mol. ofCa (NO3 2 mol. of CO (NH 2m01.0fKNO3 lf desired the content of potassium nitrate may be augmented materially by addition of potassium nitrcte produced by conversion of the calcium nitrate obtained in the process with potassium salts.

lf the phosphoric acid containing mother liquor is so apportioned that no part of the liquor is used according to reaction 2a. the phosphoric acid is exclusively obtained in the citrate soluble form as (li-calcium phosphate according to reaction (3) and a mixed product may be prepared with the entire phosphoric acid in this form., The potassium nitrate for admixture may in this case be prepared by converting the ammonium nitrate formed in the process with potassium chloride. It is evident that the composition of the product, and the ratio of components may be Widely varied.accordi-ngA to the quantity of ammonium nitrate which is used 'for lil@ isc

pound fertilizer.

conversion with potassium chlcride. .If the total quantity of ammonium nitrate is converted into potassium nitrate acccrding to reaction (4) and if the entire quantity of potassium nitrate so obtained is adiniXed, a compound fertilizer of the following composition results.

2 CIHPQ4 4: KNOB with a theoretical content of 7.5 per cent nitrogen, 19 per cent phosphoric acid, 24 per cent potash, and 15 per cent calcium oxide with a relative ratio between the three first components of 1 :2.5 3.2. If the ammonium nitrate solution is only partly converted with potassium chloride and a part of the ammonium nitrate is admixed as. such, prod- .iets for example of the following composition may be obtained:

2 2 KNOS 2 Nil-LNOs be transformed according to reaction (5) into a mixed fertilizer with exclusively watersoluble phosphoric acid.

The di-calcium phosphate may even, beforeit is returned for treatment with nitric acid be subjected to a treatment with ammonia or ammonium carbonate .whereby a certain quantity of di-ammonium phosphate is obtained in solution and may be used as admixture for preparing'the com- The tri-calcium phosphate I or the mixture of di-phosphate and calcium carbonate obtained by this reaction is filtered off and is returned to treatment with nitric acid together with fresh quantities cf phosphate rock. By this manner of working only a minimum of phosphatic residue needs be returned to the system.

In the process described only very simple, easily performable reactions are used. During the sequence of reactions the racting substancesand the products formed are to the greatest possible extent withdrawn from circulation. lt is even possible to avoid the returning of any components of reaction and still to obtain finished products of desired composition and well-balanced rati-o of components. rihe process is therefore exceedingly economical and accommodable and offers considerable advantages as compared with prior methods. An important merit is to be seen in the fact that the reactions may be carried out in relatively concentrated solutions, so that evaporation costs are reduced to a minimum.

Instead of lusing potassium chloride for preparing the potassium nitrate from the ammonium nitrate solution, potassium sulphate may serve for said purpose. The choice of potassium salt to be used is essentially a question of market prices. As is well known, the reaction of ammonium nitrate with potassium sulphate is most convenientlv` carried out in presence of free nitric acid, whereby ammonium sulphate or ammonium sulphate-nitrate is formed and leaves the process.

Besides by conversion of the ammonium nitrate available in the process, potassium nitrate may be prepared from the ycalcium nitrate, resulting in the reactions 2dr/land 2b. by conversion withipotassium sulphate or chloride.

Iclaim:

l. A process of manufacturing concentrated universal fertilizers, comprising dissolving phosphate rockin nitric acid to form a solution containing calcium nitrate and free phosphoric acid, dividing the solution so obtained into two portions, cystallizing from the first of said portions as much as possible of the calcium nitrate present, and separating the crystals from the remaining mother liquor, subjecting also the second portion of the initial solution to crystallization of calcium nitrate but only to such extent that sufficient lime in the shape of nitrate is retained in solution to form di-calcium phosthe solution by means of potassium salts into potassium nitrate, which is crystallized out and asolution of ammonium salt, separating the potassium nitrate crystals from said solution, adding said potassium nitrate to the Vfirst portion of mother liquor poor in calcium nitrate, neutralizing the mixture with ammonia and bringing the product to dryness.

2. A process of manufacturing concentrated universal fertilizers, comprising dissolving phosphate rock in nitric acid to form a solution containing calcium nitrate and free phosphoric acid, dividing the solution so ios iis

obtained into two portions, crystallizingv I from the first of said portions as much as possible of the .calcium nitrate present, separating the crystals from the mother liquor, removing from said mother liquor the rest of calcium by precipitation as calcium sulphate, subjecting the second portion of the initial solution to crystallization of calcium nitrate to such extent thatsuicient calcium nitrate is retained in solution to form di-calcium phosphate with the phosphoric acid 'n present, separating'the crystals of calcium nitrate from the solution, adding ammonia to the latter to precipitate di-calcium phosphate and to give a solution of ammonium nitrate, separating di-calcium phosphate lo from the solution, converting the ammonium nitrate of the solution by means of potassium salts into potassium nitrate, which crystallizes out, and a solution of ammonium salt, separating the potassum nitrate crystals 115 from said solution, adding said potassium nitrate to the first portion of mother liquor free from calcium nitrate, neutralizing the mixed liquor with ammonia and bringing the product to dryness.

3. A. process of manufacturing concentrated universal fertilizers, comprising dissolving phosphate rock in nitric acid to term a solution containing calcium nitrate and free phosphoric acid, dividing the .solution so obtained into two portions, crystallizing from the irst of said portions as much as possible of the calcium nitrate present, separating the crystals from the mother liquor, subjectingr the second portion of the initial solution to crystallization of calcium nitrate to such extent that sufficient calcium nitrate is retained in solution to form di-calcium phosphate with the phosphoric acid present, separating the calcium nitrate crystals from the solution, adding ammonia to the latter to precipitate di-calcium phosphate 'and to give a solution of ammonium nitrate, separating di-calcium phosphate from the solution, converting tie ammonium nitrate of the solution by means of a potassium salt into potassium nitrate Which crystallizes out neraeor to precipitate cli-calcium phosphate and to give a solution of ammonium nitrate, separating di-calcium phosphate from the solution, converting the ammonium nitrate of the solution by means oi a potassium salt into potassium nitrate which crystallizes out and a solution of ammonium salt, separating the potassium nitrate crystals from said solution, y

ERLlNG JOHNSON.

and a solution of ammonium salt, separating i the potassium nitrate crystals from said solution, adding said potassium nitrate to the first portion of mother liquor poor in calcium nitrate and neutralizing the mixed liquor with ammonia by distribution in an atmosphere of ammonia gas for obtaining immediately a dry, neutralized product.

la A process of manufacturing concentrated universal fertilizers, comprising dissolving phosphate roclr in nitric acid to form a solution containing calcium nitrate and tree phosphoric acid, dividing the tained into two portions, crystallizing from the first of said portions as much as possible of the calcium nitrate present, separating the crystals from the mother liquor, subjecting the second portion of the initial solution to crystallization of calcium nitrate to such extent that sucient calcium nitrate is retained in solution to form di-calcium phosphate with the phosphoric acid present, separating the crystals of calcium nitrate from the solution, adding ammonia to the latter solution so ob- 

